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Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.


Related in: MedlinePlus

Demonstration of biosensor chamber push-wash and pull-evacuation for an immunoassay.(i) Yellow (representing test sample containing target antigen), Red (representing blocking solution), Blue (representing fluorescent labelled secondary antibodies) liquids, and de-ionized water (representing washing solution) are respectively loaded into biosensor chamber B, source chambers A1 and A2, washing solution chamber C. (ii—vi) Yellow liquid is pull-evacuated into waste chamber W, wash solution chamber is sealed and biosensor chamber is washed twice. (vii—xi) Red liquid is burst into biosensor chamber B, followed by a rinse and a wash of the biosensor chamber B. (xii—xvii) Blue liquid is burst into biosensor chamber B, followed by a rinse and a double volume wash of the biosensor chamber B.
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pone.0121836.g005: Demonstration of biosensor chamber push-wash and pull-evacuation for an immunoassay.(i) Yellow (representing test sample containing target antigen), Red (representing blocking solution), Blue (representing fluorescent labelled secondary antibodies) liquids, and de-ionized water (representing washing solution) are respectively loaded into biosensor chamber B, source chambers A1 and A2, washing solution chamber C. (ii—vi) Yellow liquid is pull-evacuated into waste chamber W, wash solution chamber is sealed and biosensor chamber is washed twice. (vii—xi) Red liquid is burst into biosensor chamber B, followed by a rinse and a wash of the biosensor chamber B. (xii—xvii) Blue liquid is burst into biosensor chamber B, followed by a rinse and a double volume wash of the biosensor chamber B.

Mentions: The demonstration of how biosensor chamber push-wash and pull-evacuation for an antigen detection immunoassay can be implemented on the microfluidic CD is shown in Fig 5. Fig 5(i) illustrates the initiation of the test with the loading of biosensor chamber B and source chambers A1 & A2 with 60μL of Yellow, Red and Blue colored liquids respectively, and the washing solution chamber C with 420 μL of de-ionized water. To relate this to an actual antigen detection fluorescent immunoassay, imagine that the CD is made of black PMMA material, biosensor chamber B is pre-coated with capture antibodies, Yellow liquid represents test samples containing the target antigen, Red liquid represents the blocking solution, and Blue liquid represents the fluorescently labelled secondary antibodies. The sequence of the immunoassay is then as follows: the test sample containing the target antigen is pull-evacuated into waste chamber W, and biosensor chamber B is then push-washed twice; next the blocking solution is burst into biosensor chamber B and is then pull-evacuated into waste chamber W followed by push-washes; finally the fluorescent labelled antibody solution is burst into biosensor chamber B and subsequently pull-evacuated into waste chamber W, and then the biosensor chamber is push-washed twice. Note that for simplicity in the discussion, incubation steps are not included, but should be included in an actual immunoassay [16].


Sequential push-pull pumping mechanism for washing and evacuation of an immunoassay reaction chamber on a microfluidic CD platform.

Thio TH, Ibrahim F, Al-Faqheri W, Soin N, Kahar Bador M, Madou M - PLoS ONE (2015)

Demonstration of biosensor chamber push-wash and pull-evacuation for an immunoassay.(i) Yellow (representing test sample containing target antigen), Red (representing blocking solution), Blue (representing fluorescent labelled secondary antibodies) liquids, and de-ionized water (representing washing solution) are respectively loaded into biosensor chamber B, source chambers A1 and A2, washing solution chamber C. (ii—vi) Yellow liquid is pull-evacuated into waste chamber W, wash solution chamber is sealed and biosensor chamber is washed twice. (vii—xi) Red liquid is burst into biosensor chamber B, followed by a rinse and a wash of the biosensor chamber B. (xii—xvii) Blue liquid is burst into biosensor chamber B, followed by a rinse and a double volume wash of the biosensor chamber B.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4390340&req=5

pone.0121836.g005: Demonstration of biosensor chamber push-wash and pull-evacuation for an immunoassay.(i) Yellow (representing test sample containing target antigen), Red (representing blocking solution), Blue (representing fluorescent labelled secondary antibodies) liquids, and de-ionized water (representing washing solution) are respectively loaded into biosensor chamber B, source chambers A1 and A2, washing solution chamber C. (ii—vi) Yellow liquid is pull-evacuated into waste chamber W, wash solution chamber is sealed and biosensor chamber is washed twice. (vii—xi) Red liquid is burst into biosensor chamber B, followed by a rinse and a wash of the biosensor chamber B. (xii—xvii) Blue liquid is burst into biosensor chamber B, followed by a rinse and a double volume wash of the biosensor chamber B.
Mentions: The demonstration of how biosensor chamber push-wash and pull-evacuation for an antigen detection immunoassay can be implemented on the microfluidic CD is shown in Fig 5. Fig 5(i) illustrates the initiation of the test with the loading of biosensor chamber B and source chambers A1 & A2 with 60μL of Yellow, Red and Blue colored liquids respectively, and the washing solution chamber C with 420 μL of de-ionized water. To relate this to an actual antigen detection fluorescent immunoassay, imagine that the CD is made of black PMMA material, biosensor chamber B is pre-coated with capture antibodies, Yellow liquid represents test samples containing the target antigen, Red liquid represents the blocking solution, and Blue liquid represents the fluorescently labelled secondary antibodies. The sequence of the immunoassay is then as follows: the test sample containing the target antigen is pull-evacuated into waste chamber W, and biosensor chamber B is then push-washed twice; next the blocking solution is burst into biosensor chamber B and is then pull-evacuated into waste chamber W followed by push-washes; finally the fluorescent labelled antibody solution is burst into biosensor chamber B and subsequently pull-evacuated into waste chamber W, and then the biosensor chamber is push-washed twice. Note that for simplicity in the discussion, incubation steps are not included, but should be included in an actual immunoassay [16].

Bottom Line: However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps.The proposed technique is demonstrated on two CD designs.The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber.

View Article: PubMed Central - PubMed

Affiliation: Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Centre for Innovation in Medical Engineering, Department of Biomedical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia; Faculty of Science, Technology, Engineering and Mathematics, INTI International University, Persiaran Perdana BBN, Putra Nilai, 71800 Nilai, Negeri Sembilan, Malaysia.

ABSTRACT
A centrifugal compact disc (CD) microfluidic platform with reservoirs, micro-channels, and valves can be employed for implementing a complete immunoassay. Detection or biosensor chambers are either coated for immuno-interaction or a biosensor chip is inserted in them. On microfluidic CDs featuring such multi-step chemical/biological processes, the biosensor chamber must be repeatedly filled with fluids such as enzymes solutions, buffers, and washing solutions. After each filling step, the biosensor chamber needs to be evacuated by a passive siphoning process to prepare it for the next step in the assay. However, rotational speed dependency and limited space on a CD are two big obstacles to performing such repetitive filling and siphoning steps. In this work, a unique thermo-pneumatic (TP) Push-Pull pumping method is employed to provide a superior alternative biosensor chamber filling and evacuation technique. The proposed technique is demonstrated on two CD designs. The first design features a simple two-step microfluidic process to demonstrate the evacuation technique, while the second design shows the filling and evacuation technique with an example sequence for an actual immunoassay. In addition, the performance of the filling and evacuation technique as a washing step is also evaluated quantitatively and compared to the conventional manual bench top washing method. The two designs and the performance evaluation demonstrate that the technique is simple to implement, reliable, easy to control, and allows for repeated push-pulls and thus filling and emptying of the biosensor chamber. Furthermore, by addressing the issue of rotational speed dependency and limited space concerns in implementing repetitive filling and evacuation steps, this newly introduced technique increases the flexibility of the microfluidic CD platform to perform multi-step biological and chemical processes.

No MeSH data available.


Related in: MedlinePlus